Method of manufacturing assembly for plasma reaction chamber and use thereof

ABSTRACT

An electrode assembly for a plasma reaction chamber wherein processing of a semiconductor substrate such as a single wafer can be carried out, a method of manufacture of the electrode assembly and a method of processing a semiconductor substrate with the assembly. The electrode assembly includes a support member such as a graphite ring, an electrode such as a silicon showerhead electrode in the form of a circular disk of uniform thickness and an elastomeric joint between the support member and the electrode. The elastomeric joint allows movement between the support member and the electrode to compensate for thermal expansion as a result of temperature cycling of the electrode assembly. The elastomeric joint can include an electrically and/or thermally conductive filler and the elastomer can be a catalyst-cured polymer which is stable at high temperatures.

This application is a continuation of application Ser. No. 09/629,457,filed Jul. 31, 2000 (now U.S. Pat. No. 6,194,322 B1), which is adivisional of application Ser. No. 09/392,265, filed Sep. 9, 1999 (nowU.S. Pat, No. 6,148,765), which is a continuation of application Ser.No. 09/107,471, filed Jun. 30, 1998 (now U.S. Pat. No. 6,073,577).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to an apparatus for plasma processing ofsemiconductor wafers, and more particularly, to an electrode assemblywherein the electrode is bonded to a support member. The invention alsorelates to a process of assembling the electrode and processing of asemiconductor substrate with the electrode assembly.

2. Description of the Related Art

Electrodes used in plasma processing reactors for processingsemiconductor substrates such as silicon wafers are disclosed in U.S.Pat. Nos. 5,074,456 and 5,569,356, the disclosures of which are herebyincorporated by reference. The '456 patent discloses an electrodeassembly for a parallel plate reactor apparatus wherein the upperelectrode is of semiconductor purity and bonded to a support frame byadhesive, solder, or brazing layer. The soldering or brazing layer canbe low vapor pressure metals such as indium, silver and alloys thereofand the bonded surfaces of the support frame and the electrode can becoated with a thin layer of metal such as titanium or nickel to promotewetability and adhesion of the bonding layer. It has been found thatmetallurgical bonds such as In bonds cause the electrode to warp due todifferential thermal expansion/contraction of the electrode and the partto which the electrode is bonded. It has also been found that thesemetallurgical bonds fail at high plasma processing powers due to thermalfatigue and/or melting of the bond.

Dry plasma etching, reactive ion etching, and ion milling techniqueswere developed in order to overcome numerous limitations associated withchemical etching of semiconductor wafers. Plasma etching, in particular,allows the vertical etch rate to be made much greater than thehorizontal etch rate so that the resulting aspect ratio (i.e., theheight to width ratio of the resulting notch) of the etched features canbe adequately controlled. In fact, plasma etching enables very finefeatures with high aspect ratios to be formed in films over 1 micrometerin thickness.

During the plasma etching process, a plasma is formed above the maskedsurface of the wafer by adding large amounts of energy to a gas atrelatively low pressure, resulting in ionizing the gas. By adjusting theelectrical potential of the substrate to be etched, charged species inthe plasma can be directed to impinge substantially normally upon thewafer, wherein materials in the unmasked regions of the wafer areremoved.

The etching process can often be made more effective by using gases thatare chemically reactive with the material being etched. So called“reactive ion etching” combines the energetic etching effects of theplasma with the chemical etching effect of the gas. However, manychemically active agents have been found to cause excessive electrodewear.

It is desirable to evenly distribute the plasma over the surface of thewafer in order to obtain uniform etching rates over the entire surfaceof the wafer. For example, U.S. Pat. Nos. 4,595,484, 4,792,378,4,820,371, 4,960,488 disclose showerhead electrodes for distributing gasthrough a number of holes in the electrodes. These patents generallydescribe gas distribution plates having an arrangement of aperturestailored to provide a uniform flow of gas vapors to a semiconductorwafer.

A reactive ion etching system typically consists of an etching chamberwith an upper electrode or anode and a lower electrode or cathodepositioned therein. The cathode is negatively biased with respect to theanode and the container walls. The wafer to be etched is covered by asuitable mask and placed directly on the cathode. A chemically reactivegas such as CF₄, CHF₃, CCIF₃ and SF₆ or mixtures thereof with O₂, N₂, Heor Ar is introduced into the etching chamber and maintained at apressure which is typically in the millitorr range. The upper electrodeis provided with gas holes which permit the gas to be uniformlydispersed through the electrode into the chamber. The electric fieldestablished between the anode and the cathode will dissociate thereactive gas forming a plasma. The surface of the wafer is etched bychemical interaction with the active ions and by momentum transfer ofthe ions striking the surface of the wafer. The electric field createdby the electrodes will attract the ions to the cathode, causing the ionsto strike the surface in a predominantly vertical direction so that theprocess produces well-defined vertically etched side walls.

A showerhead electrode 10 in an assembly for a single wafer etcher isshown in FIG. 1. Such a showerhead electrode 10 is typically used withan electrostatic chuck having a flat bottom electrode on which a waferis supported spaced 1 to 2 cm below the electrode 10. Such chuckingarrangements provide temperature control of the wafer by supplyingbackside He pressure which controls the rate of heat transfer betweenthe wafer and the chuck.

The electrode assembly is a consumable part which must be replacedperiodically. Because the electrode assembly is attached to atemperature-controlled member, for ease of replacement, it has beenconventional to metallurgically bond the upper surface of the outer edgeof the silicon electrode 10 to a graphite support ring 12 with indiumwhich has a melting point of about 156° C. Such a low melting pointlimits the amount of RF power which can be applied to the electrodesince the RF power absorbed by the plasma causes the electrode to heatup. The electrode 10 is a planar disk having uniform thickness fromcenter to edge thereof. An outer flange on ring 12 is clamped by analuminum clamping ring 16 to an aluminum temperature-controlled member14 having water cooling channels 13. Water is circulated in the coolingchannels 13 by water inlet/outlet connections 13 a. A plasma confinementring 17 comprised of a stack of spaced-apart quartz rings surrounds theouter periphery of electrode 10. The plasma confinement ring 17 isbolted to a dielectric annular ring 18 which in turn is bolted to adielectric housing 18 a. The purpose and function of confinement ring 17is to cause a pressure differential in the reactor and increase theelectrical resistance between the reaction chamber walls and the plasmathereby confining the plasma between the upper and lower electrodes. Aradially inwardly extending flange of clamping ring 16 engages the outerflange of graphite support ring 12. Thus, no clamping pressure isapplied directly against the exposed surface of electrode 10.

Process gas from a gas supply is supplied to electrode 10 through acentral hole 20 in the temperature-controlled member 14. The gas then isdistributed through one or more vertically spaced apart baffle plates 22and passes through gas distribution holes (not shown) in the electrode10 to evenly disperse the process gas into reaction chamber 24. In orderto provide enhanced heat conduction from electrode 10 totemperature-controlled member 14, process gas can be supplied to fillopen spaces between opposed surfaces of temperature-controlled member 14and support ring 12. In addition, gas passage 27 connected to a gaspassage (not shown) in the annular ring 18 or confinement ring 17 allowspressure to be monitored in the reaction chamber 24. To maintain processgas under pressure between temperature-controlled member 14 and supportring 12, a first O-ring seal 28 is provided between an inner surface ofsupport ring 12 and an opposed surface of temperature-controlled member14 and a second O-ring seal 29 is provided between an outer part of anupper surface of support ring 12 and an opposed surface of member 14. Inorder to maintain the vacuum environment in chamber 24, additionalO-rings 30, 32 are provided between temperature-controlled member 14 andcylindrical member 18 b and between cylindrical member 18 b and housing18 a.

The process of bonding the silicon electrode 10 to the support ring 12requires heating of the electrode to a bonding temperature which maycause bowing or cracking of the electrode due to the different thermalcoefficients of expansion of the silicon electrode 10 and the graphitering 12. Also, contamination of wafers could result from solderparticles or vaporized solder contaminants deriving from the jointbetween electrode 10 and ring 12 or from the ring itself. Duringhigh-power plasma processing, the temperature of the electrode may evenbecome high enough to melt the solder and cause part or all of theelectrode 10 to separate from the ring 12. However, even if theelectrode 10 becomes partly separated from ring 12, local variations inelectrical and thermal power transmission between ring 12 and electrode10 could result in nonuniform plasma density beneath the electrode 10.

SUMMARY OF THE INVENTION

The invention provides an electrode assembly for use in a plasmareaction chamber for semiconductor substrate processing. The electrodeassembly includes a support member having a bonding surface, an RFdriven electrode and an elastomeric joint therebetween. The electrodehas an exposed surface which is intended to face the semiconductorsubstrate to be processed in the reaction chamber and a bonding surfaceat an outer edge of the electrode joined to the bonding surface of thesupport member by the elastomeric joint. The elastomeric jointcompensates for thermal mismatch and/or thermal gradients since itallows the electrode to move relative to the support member duringtemperature cycling of the assembly.

According to a preferred embodiment, the electrode comprises ashowerhead electrode and the electrode assembly is removably attached toa temperature-controlled member having a gas passage supplying a processgas to a backside of the showerhead electrode. In this case, thetemperature-controlled member optionally can include a cavity and one ormore baffle plates located in the cavity whereby the gas passagesupplies process gas into the cavity to pass through the baffles andoutlets of the showerhead electrode. A recess can be located in theelectrode and/or the support member so as to accommodate the elastomericjoint and provide a seal which extends completely around the outer edgeof the electrode. The electrode can comprise a circular silicon disk ofuniform or nonuniform thickness and the elastomeric joint can comprisean electrically conductive material having an electrically conductivefiller such as metal particles. The filler preferably provides directelectrical contact between the electrode and the support member.

The invention also provides a method of assembling an RF poweredelectrode such as a showerhead electrode useful in a plasma reactionchamber. The method includes applying an elastomeric bonding material toone or more mating surfaces of the electrode and a support member,assembling the electrode and support member and curing the bondingmaterial to form an elastomeric joint between the electrode and supportmember. The mating surfaces are preferably coated with a primer which issubsequently cured and/or the bonding material is subjected to adensifying step in a vacuum environment to remove gas bubbles prior tobeing applied to the electrode and/or the support member. In a preferredembodiment, the elastomeric bonding material is applied to a shallowrecess in a graphite support ring and a silicon electrode is pressedagainst the support ring during curing of the joint.

The invention also provides a method of processing a semiconductorsubstrate in a plasma reaction chamber. The method includes supplying asemiconductor substrate such as a wafer to the plasma reaction chamber,supplying process gas to the chamber, and processing the substrate bysupplying electrical power to an electrode assembly. The electrodeassembly includes an electrode and a support member and the electricalpower passes to the electrode through an elastomeric joint which bondsthe electrode to the support member such that the electrode movesrelative to the support member during temperature cycling of theassembly. The electrode can be a showerhead electrode and the processgas can be supplied to the chamber through a gas passage in atemperature-controlled member mounted in the plasma reaction chambersuch that the process gas passes through an exposed surface of theshowerhead electrode. The support member can be a graphite ringremovably attached to the temperature-controlled member and theelectrode can be a silicon disc joined to the graphite ring solely bythe elastomeric joint.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described with reference to thefigures, wherein:

FIG. 1 is a side sectional view of a prior art showerhead electrodeassembly for single wafer processing;

FIG. 2 is a side sectional view of a showerhead electrode assemblyaccording to one embodiment of the present invention; and

FIG. 3 is a side sectional view of a portion of the arrangement shown inFIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

The electrode assembly of the invention overcomes disadvantages of theprior art electrode assembly shown in FIG. 1 by providing betteraccommodation of stresses due to thermal mismatch between the electrodeand support member which prolongs the life of the electrode, allowingthe electrode to be exposed to higher temperatures which allows thereactor to be run at higher power, lowering the cost of production andassembly of the electrode, and providing a greater degree of flatnessfrom the center to the outer periphery of the electrode during operationof the reactor which allows uniform plasma processing of semiconductorsubstrates. The plasma processing includes etching of materials such asoxide layers, stripping of materials such as photoresists, deposition oflayers such as SiO₂, etc. The primary benefits of the invention,however, are the reduction in stress in the electrode assembly due tomismatch of coefficients of thermal expansion and/or thermal gradientsof the electrode components and allowing higher power operation of theplasma reactor.

A showerhead electrode assembly according to the present inventionincludes an electrode, a support member, and an elastomeric joint forresiliently bonding the electrode to the support member. Thus, theinvention avoids the need for solder bonding the electrode to asupporting ring which can lead to the various disadvantages discussedabove with respect to the arrangement shown in FIG. 1.

Because the electrode assembly is a consumable part which must beperiodically replaced, the electrode is preferably bonded to a supportmember in the form of a ring which can be mechanically clamped to apermanent part of the reactor. For instance, the ring of the electrodeassembly can be removably attached to a temperature-controlled memberhaving a gas passage for providing process gas (e.g., a suitable plasmaetching gas for etching silicon dioxide or other layer of material onthe wafer) which passes into a cavity containing baffle plates andoutwardly through outlets in the electrode. If desired, however, theelectrode assembly can have other arrangements wherein the electrode isnot a showerhead electrode and/or the support member is not in the formof a ring. For instance, the electrode could be a showerhead electrodebonded to a backing plate having gas distribution holes communicatingwith those in the electrode. Another possibility is where the electrodeis bonded to a support member in the form of a plate, cylinder,projections on a base member, etc.

According to the preferred embodiment of the invention, the supportmember is in the form of a ring having a radially outwardly extendingflange at one edge thereof for removably attaching the electrodeassembly to a temperature-controlled member located in the interior of aplasma reaction chamber such as the type used for single wafer plasmaetching. In the assembled condition, cooling channels in the uppersurface of the temperature-controlled member can provide water coolingof the electrode assembly.

The electrode preferably consists of an electrically conductive materialsuch as a planar silicon (e.g., single crystal silicon), graphite orsilicon carbide electrode disc having uniform thickness from the centerto the outer edge thereof. However, electrodes having nonuniformthickness, different materials and/or without process gas distributionholes could also be used with the electrode assembly according to theinvention. In a preferred embodiment, the electrode is a showerheadelectrode provided with a plurality of spaced apart gas dischargepassages which are of a size and distribution suitable for supplying aprocess gas which is energized by the electrode and forms a plasma inthe reaction chamber beneath the electrode. However, any type ofelectrode useful in a plasma reactor or vacuum environment can be usedas part of the electrode assembly according to the invention, suchelectrodes including sputter electrodes.

The elastomeric joint can comprise any suitable elastomeric materialsuch as a polymer material compatible with a vacuum environment andresistant to thermal degradation at high temperatures such as above 200°C. The elastomer material can optionally include a filler ofelectrically and/or thermally conductive particles or other shapedfiller such as wire mesh, woven or non-woven conductive fabric, etc.Polymeric materials which can be used in plasma environments above 160°C. include polyimide, polyketone, polyetherketone, polyether sulfone,polyethylene terephthalate, fluoroethylene propylene copolymers,cellulose, triacetates, silicone, and rubber. Examples of high purityelastomeric materials include one-component room temperature curingadhesives available from General Electric as RTV 133 and RTV 167, aone-component flowable heat-curable (e,g. over 100° C.) adhesiveavailable from General Electric as TSE 3221, and a two-part additioncure elastomer available from Dow Corning as “SILASTIC.” An especiallypreferred elastomer is a polydimethylsiloxane containing elastomer suchas a catalyst cured, e.g. Pt-cured, elastomer available from Rhodia asV217, an elastomer stable at temperatures of 250° C. and higher.

In the case where the elastomer is an electrically conductive elastomer,the electrically conductive filler material can comprise particles of aan electrically conductive metal or metal alloy. A preferred metal foruse in the impurity sensitive environment of a plasma reaction chamberis an aluminum alloy such as a 5-20 weight % silicon containing aluminumbase alloy. For example, the aluminum alloy can include about 15 wt %silicon.

In order to stay within the elastic limits of the finally formed joint,it has been found useful to provide one or more recesses in at least oneof the members to be attached. That is, too thin of a joint could tearduring thermal cycling whereas too thick a joint could affect electricalpower transmission and/or thermal coupling between the parts to bejoined. In the case of attaching a silicon electrode to a graphitesupport ring, a recess can be provided in the graphite ring for purposesof maintaining a thin enough layer of elastomer between the electrodeand support ring to provide adequate electrical coupling yet thickenough to accommodate thermal mismatch between the electrode and supportring. As an example, in the case of a thermally conductive elastomerhaving a filler content of about 45 to 55 volume % and an average fillerparticle size of 0.7 to 2 μm, the recess can have a depth of about 2mils (about 50 μm). In contact areas surrounding the recess, theelastomer is thin enough to provide higher electrical conductivity thanexhibited by the bulk elastomer because individual particles bridge theopposed contact surfaces. In addition, the combination of suitably sizedparticles and groove depth allows the passage of RF current through thejoint. If the filler content is increased to above 65 to 70 volume % forproviding a better DC path through the joint, such high filler contentscould adversely affect the elasticity of the joint. However, it is notnecessary to use an electrically and/or thermally conductive elastomersince sufficient RF power can be supplied to the electrode through athin area of the elastomeric joint due to capacitive coupling betweenthe electrode and the support member. Such a thin joint also providesadequate thermal conductivity between the electrode and the supportmember.

The mating surfaces of the electrode and support member can be planar ornon-planar. For instance, one mating surface can be planar and the othercan include a recess for receiving the bonding material as describedabove. Alternatively, the mating surfaces can be contoured to provide aninterlocking and/or self-aligning arrangement. In order to enhanceadhesion of the elastomeric bonding material, the mating surfaces arepreferably coated with a suitable primer. If the bonding material is theV217 material described above, the primer can be a siloxane in analiphatic solvent such as Rhodia's VI-SIL V-06C.

The primer can be applied as a thin coating by any suitable techniquesuch as wiping, brushing, spraying, etc. to create bonding sites on themating surfaces for the later applied bonding material. If the primercontains a solvent, application of the primer by wiping can enhancebonding by cleaning the mating surfaces. A siloxane containing primerreacts with air and creates Si bonding sites when cured in air at roomtemperature. Such primers provide a visual indication of the amount ofbonding sites with excessive primer locations appearing powdery.Although the primer provides an easy and effective technique forconditioning the mating surfaces, other conditioning techniques such astreating the surfaces in an oxygen plasma can be used.

In order to provide a good quality elastomeric joint, it is desirable todensify the elastomer bonding material prior to applying it to themating surfaces. For example, the elastomer bonding material can besubjected to vibration in a vacuum environment at ambient or elevatedtemperature. A vacuum pressure below 1 Torr, preferably below 500 mTorrcan be used to degas the bonding material. The vacuum can be pulsed byventing one or more times during the densifying treatment to enhancebreakup of bubbles generated by the vacuum. As an example, a vacuum ofabout 200 mTorr can be pulsed 4 or 5 times over a 30 minute period oftime. The presence of filler in the elastomeric bonding material alsoaids in breaking up the bubbles formed in the vacuum. Without theagitation/pulsed vacuum, the elastomer bonding material expands undervacuum to about 10 times its starting volume, thus creating storage andcleanup problems which can introduce new air pockets into the material.Such gas sites could form bubbles during curing of the bonding material,thus degrading the finally formed joint.

Masking of the mating surfaces provides a useful way of protecting thesurrounding surfaces and removing excess bonding material after thejoint is formed. For the highly pure materials used as components ofplasma reactors, polyester and/or polyimide materials such as MYRLAR andKAPTON tapes having silicon/graphite compatible adhesive can be used. Inthe case of a silicon showerhead electrode, it is desirable to cover thegas outlets on the electrode with MYLAR tape and the outside edge of theelectrode can be covered with a strip of KAPTON tape. In the case of agraphite support ring, the inner and outer edges can be covered withstrips of KAPTON tape. In order to aid removal of excess bondingmaterial after the joint is formed, it is useful to apply primer to themasking material to promote sticking of the elastomer bonding materialthereto. In this way, when the masking material is removed from thebonded parts, the excess bonding material adhered to the maskingmaterial is also removed.

The elastomeric bonding material can be applied to one or both of themating surfaces. In the case of a silicon electrode and graphite supportring, it is desirable to apply the bonding material to the graphitesupport ring because it is more porous. For example, a bead of thebonding material can be applied into a recess extending completelyaround the support ring. The amount of the bonding material preferablyexceeds the volume of the finally formed joint. As an example, thebonding material can be applied in an amount of about 5 times the amountneeded to form the joint.

After the bonding material is applied to at least one of the matingsurfaces, the bonding material can be subjected to a densifying step.For instance, the graphite ring with the bonding material appliedthereto can be placed in a vacuum environment as described earlier toremove gas bubbles introduced during the step of applying the bondingmaterial.

After the bonding material is applied to at least one of the matingsurfaces, the parts can be assembled such that the mating surfaces arepressed together. In the case of the electrode and support ringdescribed above, the electrode can be held in a fixture and plastic pinsof the fixture can be used to guide the support ring into precisecontact with the electrode. Initially, slight pressure such as handpressure can be used to spread the elastomer throughout the joint to beformed. After the elastomer is spread, a static load such as a 30 poundweight can be applied to the electrode during curing of the bond.

The bond can be cured at ambient or elevated temperature in anatmospheric or protective gas environment. For example, the assembly canbe placed in a convection oven and heated to a low temperature toaccelerate curing of the bond without inducing thermal strains into theparts to be joined. In the case of the electrode and support ringdescribed above, it is desirable to maintain the temperature below 60°C., e.g. 45 to 50° C. for a suitable time, e.g. 3 to 5 hours.

After the bond is cured to form the elastomeric joint, the assembly iscooled and the masking material is removed. Further, any additionalcleanup and/or further manufacturing steps such as outgassing in avacuum oven can be carried out depending on the requirements of theassembly operation.

FIG. 2 shows a showerhead electrode arrangement 40 in accordance withone embodiment of the invention. The electrode arrangement 40 includesan electrode 42 and an electrically conductive support ring 44. Theelectrode assembly can be substituted for the electrode assemblyconstituted by electrode 10 and support ring 12 shown in FIG. 1. Theelectrode 40 differs from the In-bonded assembly shown in FIG. 1 in thatthe electrode 42 is bonded to the support ring 44 by an elastomericjoint 46 which can be located in a recess 48, as shown in FIG. 3.

In accordance with an embodiment of the invention, the recess 48 extendscontinuously around the support ring 44 between an inner wall (notshown) and an outer wall 50 of the support ring 44. Each wall 50 can beas thin as possible, e.g. about 30 mils wide, which allows the elastomerto form a thin layer (e.g. about 2 μm thick in the case where theelastomer includes 0.7 to 2 μm sized filler) in the area in contact witheach wall 50 and a thicker layer (e.g. about 0.0025 inch) in the recess48. The recess formed by the walls can be extremely shallow, e.g. about2 mils deep, which provides a very thin elastomeric joint having enoughstrength to adhesively bond the electrode to the support ring yet allowmovement of the electrode relative to the support ring duringtemperature cycling of the electrode assembly. Additionally, the wallsof the recess can protect the elastomeric joint from attack by theplasma environment in the reactor.

The electrode assembly dimensions can be adapted to meet the demands ofthe intended use of the electrode assembly. As an example, if theelectrode is used to process an 8 inch wafer, the electrode can have adiameter slightly less than 9 inches and the support ring can have awidth at the interface between the electrode and the support ringslightly less than 0.5 inch. For example, the support ring at theinterface can have an inner diameter of 8 inches and an outer diameterat the interface of 8.8 inches. In such a case, the interface betweenthe electrode and support ring can have a width of about 0.4 inch andthe recess can have a width of 0.34 inch if the walls are 0.030 inchwide.

While a specific example of a joint has been described, otherelastomeric joints can be utilized to attach the electrode to a supportmember in the form of a support ring or other configuration providedthat the joint has sufficient strength under the elevated temperatureand plasma conditions experienced in a plasma reactor environment. Theelastomeric joint preferably is vacuum compatible, has sufficienttoughness, tear strength, elasticity, resistance to thermal degradation,thermal conductivity and/or electrical conductivity. In the case wherethe electrode is a showerhead electrode, the elastomeric joint must beable to withstand the weight of the electrode and gas pressure of theprocess gas supplied to the showerhead electrode.

According to the invention, use of an elastomer material to attach theelectrode to the support ring offers advantages compared to indiumbonded electrodes with respect to reduced likelihood of breakage ofelectrode, reduced likelihood of debonding of electrode from supportring due to thermal fatigue, reduced distortion and thus improvedthermal contact between the support ring and the temperature-controlledmember during temperature cycling of the electrode assembly, improvedelectrical power supply to the electrode by maintaining good capacitivecoupling/electrical contact between electrode and support ring, reducedchamber contamination from particles or impurities and/or increasedpower capability due to the ability of the electrode assembly towithstand higher temperatures.

The apparatus according to the invention is useful for wafer processingsuch as plasma etching, deposition, etc., in multiple or single waferprocessing. For instance, the apparatus can be used for etching ordepositing BPSG, oxides such as thermal silicon dioxide or pyrolyticoxides and photoresist materials. The apparatus can maintain desirablelevels of submicron contact profile, CDs and low particle contamination.With respect to etching BPSG, etch rates of about 8000 Å/min can beachieved and etch uniformity can be maintained at around 4% forelectrode lifetimes of greater than 30,000 RF minutes, whereas In-bondedelectrode assemblies may require replacement as early as 2400 RFminutes. Photoresist etch rates of about 800 Å/min can be maintainedwhile etching silicon dioxide at about 6000 Å/min. With respect to CDline measurement, measurements by SEM of wafers etched for 200 secondsto provide vias in silicon dioxide can provide center and edge CDs lessthan 0.02 μm.

The foregoing has described the principles, preferred embodiments andmodes of operation of the present invention. However, the inventionshould not be construed as being limited to the particular embodimentsdiscussed. Thus, the above-described embodiments should be regarded asillustrative rather than restrictive, and it should be appreciated thatvariations may be made in those embodiments by workers skilled in theart without departing from the scope of the present invention as definedby the following claims.

What is claimed is:
 1. A method of manufacturing an assembly for use ina plasma reaction chamber, comprising: applying an elastomeric bondingmaterial to one or more mating surfaces of a first member and a secondmember; forming an assembly of the first member and the second membersuch that the elastomeric bonding material joins the mating surfaces ofthe first member and the second member; and curing the elastomericbonding material so as to form an elastomeric joint between the firstmember and the second member, the elastomeric joint allowing movement ofthe first member relative to the second member during temperaturecycling thereof.
 2. The method of claim 1, further comprising preparingthe elastomeric bonding material by mixing at least two components of anelastomer with an optional electrically conductive filler and densifyingthe elastomeric bonding material in a vacuum environment at ambient or atemperature above or below ambient.
 3. The method of claim 1, furthercomprising applying masking material to surfaces of the first member andthe second member so as to leave the mating surfaces exposed andoptionally coating exposed portions of the masking material with aprimer material which removes excess elastomeric bonding materialsqueezed out of the elastomeric joint when the masking material isremoved from the first member and the second member.
 4. The method ofclaim 1, wherein the first member includes a recess, the elastomericbonding material being applied in an amount such that the elastomericjoint fills the recess and is thin enough to conduct heat between thefirst and second members.
 5. The method of claim 1, wherein theelastomeric bonding material includes an electrically conductive filler,the elastomeric bonding material being applied to the mating surfaces soas to provide substantially direct electrical contact between the firstand second members.
 6. The method of claim 1, wherein the first membercomprises silicon and the second member comprises graphite, the siliconbeing bonded to the graphite solely by the elastomeric joint.
 7. Themethod of claim 1, wherein the method includes aligning the first andsecond members in a fixture, applying pressure sufficient to forceexcess bonding material outwardly of an interface between the first andsecond members, heating the assembly in an oven at a temperature highenough to accelerate curing of the elastomeric bonding material but lowenough to minimize thermal expansion of the first and second members. 8.The method of claim 1, wherein the elastomeric bonding material isfilled into a recess sized to provide a cured elastomeric joint whichallows sufficient movement between the first and second members toprevent tearing of the joint as a result of differential thermalexpansion or contraction of the first and second members during use ofthe assembly in a plasma reactor.
 9. The method of claim 1, wherein theelastomeric bonding material has a viscosity sufficient to achieveself-leveling and spreading of the bonding material on the matingsurfaces, the method further comprising degassing the bonding materialby placing the assembly in a vacuum environment.
 10. The method of claim1, further comprising applying a primer material to the mating surfacesor plasma treating the mating surfaces.
 11. A method of processing asemiconductor substrate in a plasma reaction chamber wherein an assemblyincludes a first member bonded to a second member by an elastomericjoint, comprising: supplying a semiconductor substrate to the plasmareaction chamber; supplying process gas to an interior of the plasmareaction chamber; energizing the process gas to form a plasma used toprocess an exposed surface of the semiconductor substrate, theelastomeric joint allowing the first and second members to move relativeto each other during temperature cycling of the assembly.
 12. The methodof claim 11, wherein the semiconductor substrate comprises a siliconwafer and the method includes etching a dielectric or conductive layerof material on the wafer.
 13. The method of claim 11, wherein the methodincludes depositing a layer of material on the semiconductor substrate.14. The method of claim 11, wherein the the first member comprises anelectrode and the second member comprises a temperature-controlledmember.